The invention relates to a monitoring equipment for the quick and reliable detection of the content at least one gaseous component in a gas flow, e.g. the amount of combustible gasese in the flue gas from ordinary combustion, or from a chemical process, in which a material is heat treated through direct or indirect firing of a fuel which may form part of the material to be treated, or be added separately.
An example of such a chemical process is the so-called calcining or CO.sub.2 -expulsion from, for instance, cement raw materials, the heat treatment being performed in a reactor, the calciner and the flue gases from the calciner being used for preheating the raw material, and the gases thereafter being dedusted and discharged into the atmosphere.
If, during combustion, the fuel is not completely burnt out the flue gases will contain some combustible gases like CO and CH.sub.4 which, when mixed with oxygen-containing air, will present a risk of explosion, not least when the flue gas finally is dedusted in a electrostatic precipitator in which electrical discharges frequently occur.